Automated Preparation of Simulated Distillation Samples for ASTM Methods D2887, D7213, D7398 and D6352 using a Dual Tower 7693A and Tray System

Significance of the Topic

Automated sample preparation is essential in modern simulated distillation methods to reduce manual handling of toxic solvents, ensure consistent heating and mixing, and improve laboratory safety when analyzing complex petroleum samples such as calibration standards, vacuum gas oils and polywax materials.

Objectives and Study Overview

This study presents an automated workflow for preparing samples in compliance with ASTM methods D2887, D7213, D7398 and D6352. Using an Agilent 7693A dual tower and tray system integrated with a 7890A gas chromatograph, the goal is to streamline dilution, mixing, heating and injection steps, while maintaining high reproducibility and throughput.

Methods and Instrumentation

The key instrumentation and configuration details are:

• Agilent 7890A GC with dual 7693A towers featuring a front 5 or 10 µL syringe and a back 250 or 500 µL syringe
• 150-position heated tray with mixer and barcode reader
• G3510 multimode inlet operated in temperature programmed split mode
• Choice of Low Thermal Mass (LTM) or conventional air bath oven for rapid temperature ramps
• Use of carbon disulfide or toluene as solvents for calibration and polywax sample preparation

The system software automates vial selection, reagent addition, timed mixing, heating to preset temperatures and sample injection.

Main Results and Discussion

Automation enabled:

• Preparation of C5–C40 calibration mixtures and reference gas oil dilutions with excellent consistency as shown by overlay of 11 HVGO runs
• Automated dissolution of Polywax 500 in toluene producing symmetric fragment distribution to C80
• Dissolution of Polywax 655 with detection of fragments up to C110, demonstrating high resolving power
• Significant reduction in operator exposure and variability compared to manual protocols

Use of the LTM oven reduced analysis cycle times by 30–50% for D2887, D7213 and D7398 applications.

Benefits and Practical Applications

The automated workflow offers:

• Improved laboratory safety by minimizing manual handling of toxic solvents
• Enhanced reproducibility and precision in simulated distillation analyses
• Higher throughput with integrated tray heating and mixing
• Compatibility with a range of boiling point ranges and calibration standards

Future Trends and Opportunities

Future developments may include:

• Broader integration with data analytics and machine learning for method optimization
• Expansion of automation to additional ASTM and ISO simulated distillation protocols
• Coupling with advanced detectors for simultaneous sulfur or nitrogen speciation
• Further cycle time reduction through enhanced thermal management and real-time process monitoring

Conclusion

Automating sample preparation for simulated distillation using the 7693A dual tower and tray system with the 7890A GC delivers safe, reproducible and efficient workflows for petroleum analysis across multiple ASTM standards. These capabilities simplify complex dilution and heating steps, improve chromatographic performance and support high throughput laboratory operations.

References

1. C Wang, R Firor and P Tripp, Fast Hydrocarbon and Sulfur Simulated Distillation Using the Agilent Low Thermal Mass (LTM) System on the 7890A GC and 355 Sulfur Chemiluminescence Detector, November 2008, Agilent Technologies publication 5990-3174EN